1. Field of the Invention
The present invention relates to a modified polyorgano-siloxane having an isocyanate group at its one terminal and a process for preparing the same.
More specifically, the present invention relates to a modified polyorganosiloxane having an isocyanate group at its one terminal or terminal end which can be used as a modifier for a resin having an active hydrogen capable of reacting with the isocyanate group in order to provide the resin with low frictional properties, water repellency, oil repellency, antithrombotic properties and the like, and a process for preparing the modified polyorganosiloxane.
2. Description of the Prior Art
As polyorganosiloxanes having reactive organic groups, there are known polyorganosiloxanes having the reactive organic groups at both the terminals thereof, polyorgano-siloxanes having plural reactive organic groups on the side chains thereof, and the like. For the purpose of providing prevalent resins with water repellency, oil repellency, low frictional properties, antithrombotic properties and the like, the modification of the resins with these reactive polyorganosiloxanes has been heretofore carried out.
The simplest process for giving the above-mentioned characteristics of the polyorganosiloxane to the prevalent resins can be considered to be the polymer blend method. Further, other processes have been usually performed in which the polyorganosilxane having functional groups such as a silicon-bonding hydrogen group, silanol group, alcohol group or amino group at both the terminals thereof is used in a block copolymerization in order to introduce a polyorgano-siloxane chain into the main chain of the usual resin, thereby obtaining a block copolymer (e.g., Japanese Patent Application Laid-open Nos. 131,629/1984 and 238,315/1985).
In addition, in Japanese Patent Application Laid-open No. 189,257/1983, there is suggested a process in which an addition reaction type polyorganosiloxane is employed to form the so-called interdependent penetrating net structure (hereinafter referred to simply as IPN) from a usual thermoplastic resin and the polyorganosiloxane.
The above-mentioned polymer blend method is not practical, because the polyorganosiloxane inherently is a polymer having poor miscibility with the usual resin and therefore the polyorganosiloxane is liable to bleed on the surface of the mixture thereof.
In the block copolymerization method, the higher the content of the polyorganosiloxane, the greater the deterioration in mechanical strength which results from the polyorganosiloxane chain.
In the method in which the above-mentioned IPN is formed, the miscibility of the usual resin and the polyorganosiloxane with each other is poor, and thus it is difficult to form the uniformly distributed IPN. Therefore, if the polyorganosiloxane is not used in a high proportion at the cost of the deterioration in mechanical strength, sufficient improvement in characteristics cannot be obtained. In such a case, however, the bleeding phenomenon of the polyorganosiloxane takes place.